archiver: only store deviceID for hardlinks

The deviceID can change e.g. when backing up from filesystem snapshot.
It is only used for hardlink detection. Thus there it is not necessary
to store it for everything else.

internal/archiver/archiver.go

@@ -188,6 +188,12 @@ func (arch *Archiver) nodeFromFileInfo(snPath, filename string, fi os.FileInfo)
 	if !arch.WithAtime {
 		node.AccessTime = node.ModTime
 	}
+	if node.Links == 1 || node.Type == "dir" {
+		// the DeviceID is only necessary for hardlinked files
+		// when using subvolumes or snapshots their deviceIDs tend to change which causes
+		// restic to upload new tree blobs
+		node.DeviceID = 0
+	}
 	// overwrite name to match that within the snapshot
 	node.Name = path.Base(snPath)
 	if err != nil {

internal/archiver/archiver_test.go

@@ -2153,6 +2153,7 @@ func TestMetadataChanged(t *testing.T) {
 	sn, node2 := snapshot(t, repo, fs, nil, "testfile")
 
 	// set some values so we can then compare the nodes
+	want.DeviceID = 0
 	want.Content = node2.Content
 	want.Path = ""
 	if len(want.ExtendedAttributes) == 0 {